1. Field of the Invention
This invention relates to a method and system for surveying traffic on roadways, and particularly to an automated survey method and system capable of determining both location and size of vehicles on roadways.
2. General Description of the Prior Art
Since the early 1930's when the number of cars on American highways and in American cities began to tax the capacity of assigned vehicle routes, attempts have been made to study traffic flow with the goal of improving traffic handling facilities and maximizing the flow in existing facilities. Basic to this goal is the timely and accurate gathering of traffic flow data. Although the models arising from traffic flow studies have been vigorously and exhaustively analyzed by competent transportation experts versed in abstract mathematics, the results obtained from these studies can be no more reliable than the data from which the models were abstracted and the degree to which the models represent reality. Therefore, the problem remains primarily one of data gathering.
In the past, techniques for gathering traffic flow data have varied widely in methodology and applicability of obtained data. One method was simply to place an observer at a point of interest such as a bridge or tunnel and have the observer count the number of vehicles passing this point. Usually a count was made for six minutes and this number multiplied by ten to obtain an average hourly flow. This method has met with a fair degree of success and applicability in the study of bottlenecks and other critical points in traffic flow; however, it is obvious that to generalize point functions to the continuum of traffic flow in a district would require a prohibitively large number of personnel to provide enough sample points and sample times to achieve realiable, timely data. Other methods have sought simply to automate this counting procedure. These have included photoelectric and electromagnetic transducers for vehicle detection and the familiar air-filled hose across the road for volume of flow measurements. Speed detection has relied primarily on radar speed detectors. Whether the method is a man on the street with a manual counter or a closed circuit camera tied to a digital computer, the results are essentially the same; and the cost of a thorough, reliable study is prohibitive.
It is, accordingly, an object of the present invention to provide an improved system of gathering and processing traffic data which is thorough and reliable and at the same time is much less expensive.